Dense fog encompassing the entire midsection of the country is responsiblefor several major accidents over the weekend.Two college students were killed in a small plane crash on Sunday morning inHolland, Mich. Authorities from Allegan Country reported that the visibility inthe area was reduced to an eighth of a mile because of the dense fog.

A massive chain-reaction pile-up on I-35 near Wellsville, Kan., killed a3-year-old boy and injured at least 35 others early Saturday. Thirty vehicles,including six tractor trailers, were involved in the accident. Thick fog,decreasing visibility to a quarter mile, and icy road conditions are to blame.

Two Amish brothers were killed when a driver rear-ended the boys' buggy earlySaturday morning outside of Salem, Ind. Fog was heavy during the time of theaccident.

AccuWeather.com Facebook fans reported fog in other areas of the country aswell.

"[I] drove through some of the worst fog in a long time Saturday night aroundmidnight in Central Pennsylvania," wrote AccuWeather.com Fan Michael.

Kay of Southwest, Va., wrote that visibility was about 10-12 feet in the BlueRidge Mountains on Sunday.

AccuWeather.com meteorologists blame the thick fog on the unseasonably mildtemperatures warming the Midwest. As moist air passes over snow-covered andfrozen ground, the air is cooled and fog is formed as a result.

Become an fan of AccuWeather.com on Facebook. http://www.facebook.com/AccuWeather</a>Story by AccuWeather.com's Carly Porter.